The small, medium, and large fleet BACT schedule and obligations are given below. The percentages are the amount of fleet hp that must meet BACT by Jan 1, of that year.
So for example, if you are a large fleet and failed to meet the fleet average target on Jan 1, 2014 you would have to apply BACT to 4.8% of your fleet hp as it exists on Jan 1, 2014.
Remember that the "Year-to-year low use" and "Captive attainment area" provisions can significantly reduce your BACT obligation if they apply. For details click on the "Permanent Low Use, Year-to-Year Low Use, and Captive Attainment Fleet" box on the compliance chart.
Note that once you meet your final fleet average target you are exempt from BACT and in effect are in final compliance.